# Project Euler Problem 33

ってなったあと・・・っていうか最中に現実逃避に、
Project Eulerをやり始めた（ぉ

The fraction ^(49)/_(98) is a curious fraction, as an inexperienced mathematician in attempting to simplify it may incorrectly believe that ^(49)/_(98) = ^(4)/_(8), which is correct, is obtained by cancelling the 9s.

We shall consider fractions like, ^(30)/_(50) = ^(3)/_(5), to be trivial examples.

There are exactly four non-trivial examples of this type of fraction, less than one in value, and containing two digits in the numerator and denominator.

If the product of these four fractions is given in its lowest common terms, find the value of the denominator.

http://projecteuler.net/index.php?section=problems&id=33

ようは２桁の分数において分母と分子におんなじ数字があれば消せと。

もとの分数が同じである４つの分数の積から約分した分母の数を答えろってことらしい。

なんせ英語力がほぼ皆無のためあってるかどうか不明。

でも英語みたいなコメントで晒してみる！
ツッコミ募集（ぉ

```require 'mathn'

ans = 1

# Denominator is 2 digit.
10.upto(99) do |denominator|
# To avoid division by zero.
next if denominator % 10 == 0
# Numerator is 2 digit and less than Denominator.
10.upto(denominator-1) do |numerator|
fraction1 = numerator / denominator
fraction2 = 0
# When you require 'mathn', "Integer / Integer" is not Integer but Fraction.
# If you want to Integer, you should be Fraction#to_i.
if (denominator % 10) == (numerator / 10).to_i
fraction2 = (numerator % 10) / (denominator / 10).to_i
elsif (denominator / 10).to_i == (numerator % 10)
fraction2 = (numerator / 10).to_i / (denominator % 10)
end
ans *= fraction1 if fraction1 == fraction2
end
end

p ans.to_s
```